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STRUCTURE BACKFILL TESTING

FIELD AND LABORATORY STUDIES INDICATED THAT THE GAGE IS ABLE TO GIVE A GOOD ESTIMATE OF THE INPLACE DENSITY AND THAT WALL EFFECT IS NOT SIGNIFICANT IF THE TEST IS PROPERLY PERFORMED. FIELD CORRELATION TESTS BETWEEN SAND VOLUME AND NUCLEAR METHODS INDICATED THE SAND VOLUME TENDED TO GIVE SLIGHTLY HIGHER TEST RESULTS. LABORATORY RESEARCH ALSO INDICATED THE SAND VOLUME TENDS TO MEASURE ABOVE THE TRUE DENSITY WHEN THE DENSITY OF THE MATERIAL IS ABOVE 120 PCF. COMPARISON OF SAND VOLUME DATA FROM THE PRE-NUCLEAR ERA AND THE PRESENT NUCLEAR TESTS INDICATED THAT MORE PASSING TESTS WERE OBTAINED WITH THE SAND VOLUME TEST. THIS WAS BELIEVED DUE TO INACCURACIES OF THE SAND VOLUME TEST. THIS STUDY INDICATED THE RELATIVE COMPACTION SPECIRICATION OF 95 PERCENT SHOULD BE RETAINED. /FHWA/